The primary goal of the Mass Spectroscopy Core is to provide mass spectroscopy analyses in support of the research of the PPG investigators. To accomplish this goal, the Core will rely on existing equipment, expertise, and personnel within the Mass Spectroscopy Facilities and Service Core of the EHS Center. The range of capabilities within that Core includes: (1) molecular weight determination, (2) peptide mapping and sequencing and protein identification, (3) mapping of post-translational modifications and protein akylation sites, (4) structural elucidation of photo-crosslinked protein-nucleic acid complexes, (5) H/D exchange measurements on proteins and peptides, and (6) natural products identification and structure elucidation. The Core also designs, develops and constructs prototype instruments for specialized purposes.